The present disclosure relates to a hoist assembly. More particularly, the present disclosure relates to a hoist assembly that can be used to raise and lower a load, specifically in a theatrical setting.
Live performances in a theater typically employ a number of curtains and backdrops to convey to the audience different settings, environments, moods, and the like. These curtains and backdrops must be changed throughout the course of a performance within a fairly short timeframe without interrupting the performance. Typically this is done by raising a particular backdrop above the stage and out of sight of the audience when it is not being used. When a particular backdrop is needed, it is lowered into place on the stage.
Theatrical backdrops and curtains are typically suspended from battens, which are pipes or trusses that span the width of the stage. Battens can be 50 feet or more in length, depending on the size of the stage. As should be apparent, the weight of the battens and the items suspended from them can have substantial weight. More power is required the heavier the load being raised or lowered. Counterweights are employed to balance the load of the batten and its associated load. Battens and their associated counterweights are manually lifted and lowered. In these types of systems, a rope is tied to a counterweight and the batten is manually raised or lowered, then tied off to a pin rail mounted to a wall adjacent the stage area. However, if the load is not closely balanced, excessive energy may be required to move the load, or the system may get out of control, dropping the load or the counter-weight, causing injury, death and/or collateral damage.
Typical motorized hoists and winches have a grooved drum for winding and unwinding the cable attached to the battens. The cable leaves the drum and passes over one or more sheaves to change the orientation of the cable from the drum to the batten. The angle at which the cable pays off the drum is the fleet angle, defined as the angle between the centerline of the groove on the drum and the cable coming off the drum. The fleet angle should be kept to a minimum because increasing the fleet angle results in increased wear on the cable and drum. Therefore it is desirable to minimize the fleet angle to prolong cable and drum life.